The present invention relates to an apparatus for forming images, and more particularly to a color photocopier which irradiates an original with rays from a light source, focuses the reflection from the original as latent images on a photosensitive recording medium, and forms chromatic images corresponding to the latent images on a copy sheet.
There are three different systems generally applied to color copying machines; silver salt system, electrophotographic system, and photosensitive, pressure sensitive system. In the photosensitive, pressure sensitive system, development and transfer are accomplished by one process. A special film (photosensitive, pressure sensitive paper) with numerous microcapsules, which respond to red, green and blue lights, is exposed to imaging light and images are transferred to and fixed on a developer sheet (See U.S. Pat. No. 4,399,209).
The color electrophotographic system and the photosensitive, pressure sensitive system utilize a photosensitive recording medium with lower sensitivity than the silver salt system. In these two systems, sufficient color gradation may be not obtained only with imaging light, and thus another exposing process, i.e., supplementary exposure, is required for improving the color gradation.
For executing supplementary exposure, a device is attached in the vicinity of a region exposed to imaging light; a photosensitive drum or the whole photosensitive, pressure sensitive paper is uniformly exposed to rays emitted from the device.
The device, however, controls the color of the whole images and thus cannot change only the color of specified part of the images. The color conversion only in a specified part is sometimes required to make the part conspicuous so as to make effective photocopies; for example, the color conversion of characters or symbols in a specified part from black into a desirable color. General electrophotographic systems or photosensitive, pressure sensitive systems, however, do not have such a function.